Enhanced Load Management and Distribution System

ABSTRACT

A system for managing distribution of electrical power includes a power management circuit, power control units, a first keyline and a second keyline. The power management circuit includes a device configured to measure power consumed by an electrical load, and a comparator comparing the measured power with a power limit. Each power control unit includes an outlet for delivering power to a load; a timing control circuit coupled to each outlet and configured to deliver an enabling signal to each outlet individually with a time delay; a signal input; and a signal output. The first keyline connects the power management circuit with the signal input of one power control unit; the second keyline connects the signal output of that power control unit with the signal input of another power control unit. Each power control unit is configured to propagate a signal to another power control signal via the second keyline.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a continuation application of U.S. patentapplication Ser. No. 12/958,534, entitled “Enhanced Load Management andDistribution System” and filed on Dec. 2, 2010, the entire contents ofwhich is incorporated herein by reference.

FIELD OF THE DISCLOSURE

This disclosure relates to systems for supplying power to one or moreelectrical loads. More specifically, this invention relates to managingthe supply of power to one or more loads in a limited power environment.

BACKGROUND OF THE DISCLOSURE

Transportation systems, such as an aircraft, a ship, or a train,typically provide only a limited supply of power. This power supplyserves not only those systems that are essential, but non-essentialequipment as well. Aboard an aircraft, for example, the propulsionsystem provides a finite amount of power to operate both essentialequipment, such as life-support, communication, and flight control, andnon-essential equipment, such as coffee makers, in-flight commercialphones, in-seat entertainment centers, and a variety of devices operatedby passengers.

Because power is limited, non-essential equipment must compete withother non-essential equipment for power. If the load from non-essentialequipment exceeds the allowable load, some essential equipment may bedeprived of power. Furthermore, the power supply itself may be damagedfrom the additional loads.

Several systems and methods have been developed to monitor and adjustthe power requirements of the load, determining which equipment to turnoff and/or causing the equipment to enter a power saving mode(“load-shedding”).

U.S. Pat. Nos. 5,754,445 and 6,046,513, the disclosures of which areincorporated by reference herein in their entirety, describe a powermanagement system in which the load at consumers' outlets (where musicplayers, computing devices, etc. may be plugged in) is continuallymonitored, and certain not-in-use outlets are disabled when the systementers a power-management mode. A power management circuit is connectedto various decentralized power control units (also referred to as powersupply units or power converters) each supplying power to one or moreoutlets. A signal on a line connected to the power control units(hereafter called an ENABLE keyline) indicates whether the system is inan enabled mode or in a power-managed mode. The state of this signalenables or disables outlets that are not in use. In these systems, aconsumer device that is in use is not turned off when enteringpower-management mode.

A system as described in the above-referenced patents is shownschematically in FIG. 1. Power management circuit 1 monitors the powerconsumed by the system 3 and compares this level, using a limitcomparator 5, to the power load limit 6. The ENABLE signal istransmitted to the power control units 2 on ENABLE keyline 7; a SETcondition signifies that system power is available at the variousoutlets. When the limit comparator 5 determines that the total powersensed is below the limit, the ENABLE keyline 7 is SET. When a consumerconnects a device to an outlet 11, a request 9 for power is initiated tothe control unit. If the ENABLE keyline is SET when the request forpower is initiated, the output control 8 enables power to the deviceplugged into the outlet 11.

If the limit comparator 5 shows that the power limit has been reached,the ENABLE keyline 7 is reset to signify the additional power is notavailable. Accordingly, unused power outlets are disabled until thetotal system power consumption falls below a second threshold (asdetermined by limit comparator 5), at which time those outlets arere-enabled for use by the consumer. Should a consumer have plugged in adevice while the system was in the power management mode (so that thedevice was plugged into a disabled outlet), control latch 10 requiresthat the user unplug the device and plug it in again to initiate arequest for power. In addition, an indicator is typically provided onthe outlet to show that power is available. If the indicator isextinguished, the indicator is locked off, so that there will not be anindication that power has been restored until the device is unplugged.This is inconvenient for the consumer, since it is difficult for theconsumer to know whether power is available or has been restored inthese situations.

Systems have been devised to avoid this consumer inconvenience byautomatically connecting power to devices plugged in during a powermanagement phase. In one such system, each power control unit isprovided with timers, with a timer connected to each outlet. The timerscan impose a delay between activation of the individual outlets in thepower control unit. If the ENABLE keyline is SET when a request forpower is initiated, the output control enables power to the consumerdevice plugged into the outlet; no delay is initiated as long as poweris available when the device is plugged in. Should the consumer haveplugged in the device while the system is in the power management phase(that is, the ENABLE keyline signifies that no additional power isavailable and unused outlets are disabled), the timer limits when theoutlet may be reconnected. The timer starts a delay period during whichthe limit comparator senses the total power consumption. When the delayperiod expires, if additional power is still available the outlet isautomatically activated. The next outlet in the power control unit islikewise activated with a delay if a device was plugged in during thepower management phase; this continues until the final outlet in theunit is activated.

More recently, a system has been disclosed having specifically randomtimer action for enabling of individual outlets connected to adecentralized power supply unit. This system is shown schematically inFIG. 2. Power management circuit 42 monitors the power consumed by thesystem 44 and compares this power level to the power limit 43 usinglimit comparator 41. When the limit comparator 41 determines that thetotal power sensed is below the limit, the ENABLE keyline 33 is SET. Asa consumer connects a device to outlet 39, a request for power 38 isinitiated to the power supply unit 45. If the ENABLE keyline is SET whenthe request for power is initiated, output control 40 enables power tothe device plugged into outlet 39. No delay is initiated as long aspower is available when the device is plugged in.

If the limit comparator 41 determines that the power limit has beenreached, the ENABLE keyline 33 is reset to signify the additional poweris not available. Unused power outlets 46, 47 accordingly are disableduntil the total system power consumption falls below a second thresholdas determined by limit comparator 41 and re-enables outlets 46, 47 foruse by the consumer.

Should a consumer have plugged in while the system is in the powermanagement mode (that is, ENABLE keyline 33 signifies that no additionalpower is available and unused outlets are disabled), and subsequentlythe power consumption 44 falls below the threshold determined by limitcomparator 41, then the ENABLE keyline is SET and timers 35, 36, 37determine when each respective outlet will be reconnected. In thissystem, the timers are initiated at the same time, but cause delays ofrandom lengths at the respective outlets. As each random delay timeexpires, the associated outlet is enabled if the ENABLE keyline 33remains SET.

All of the decentralized power supply units 45, 50, etc. receive theENABLE keyline signal at the same time. All of the random timers in eachpower supply unit thus start at the same time. Since the delays are ofrandom lengths, the risk of two loads being activated simultaneously isreduced. However, in a system where multiple power supply units areattached, a number of outlets with loads still may be activated withinclose proximity in time. This may not allow enough time for the powermanagement circuit 42 to measure the consumed power and control theENABLE keyline to limit the number of outlets activated to avoid asystem overload.

In the timed automatic-connect system and random-timer system describedabove, there may be loss of control of the power load during there-connect sequence so that the system maximum is inadvertentlyexceeded. For example, laptop computers typically require severalseconds before the charging circuit reaches full current. In addition tothe device delay time, there is a period of time required for the powermanagement circuit to measure the power consumed, and for the limitcomparator to determine if additional power is available and set theENABLE keyline appropriately. If the system has several power controlunits, a number of outlets with loads may be activated simultaneously ornearly simultaneously, and thus cause overload of the power system.

The systems described just above avoid inconvenience to the consumer,but allow a potential for loss of system control and overload of thepower system. There remains a need for a load management system forlimited power environments that can re-connect devices while maintainingcontrol of the overall load.

SUMMARY OF THE DISCLOSURE

In accordance with an aspect of the disclosure, a system for managingdistribution of electrical power includes a power management circuit, aplurality of power control units, a first keyline and a second keyline.The power management circuit includes a device configured to measurepower consumed by an electrical load, and a comparator configured tocompare the measured power with a power limit. Each of the power controlunits includes at least one outlet for delivering power to a load; atiming control circuit coupled to each outlet and configured to deliveran enabling signal to each outlet individually with a time delay; asignal input; and a signal output. The first keyline connects the powermanagement circuit with the signal input of one of the power controlunits; the second keyline connects the signal output of that powercontrol unit with the signal input of another power control unit. Eachpower control unit is configured to propagate a signal to another powercontrol signal via the second keyline.

The keylines deliver either a SET or RESET signal, depending on whetherthe measured power does not exceed the limit or exceeds the limit,respectively.

In accordance with another aspect of the disclosure, a method formanaging distribution of electrical power includes measuring powerconsumed by an electrical load; comparing the measured power with apower limit; delivering one of a SET signal and a RESET signal to apower control unit, in accordance with the measured power not exceedingthe power limit and exceeding the power limit respectively; andpropagating one of the SET signal and the RESET signal, in accordancewith the signal delivered to the power control unit, to another powercontrol unit. The power control unit includes at least one outlet and atiming control circuit. The SET signal causes the timing control circuitto send an enabling signal to the outlet, thereby making power availableat the outlet; the RESET signal prevents the timing control circuit fromsending an enabling signal to an outlet not connected to a consumerdevice at initiation of the reset condition. In specific embodiments,the SET/RESET signal is delivered using a first keyline connecting onepower control unit to a power management circuit configured to performthe measuring and comparing steps, and the signal is propagated using asecond keyline connecting that power control unit to the other powercontrol unit; the first keyline is separate from the second keyline.

In accordance with another aspect of the disclosure, a method formanaging distribution of electrical power by a power system (where thesystem includes a plurality of power control units each having an outletcoupled thereto and a timing control circuit) includes measuring powerconsumed by an electrical load; comparing the measured power with apower limit to obtain a first comparison result; and, in accordance withthe first comparison result indicating the measured power exceeding thepower limit, preventing connection of an additional load to the powersystem. Subsequently, the measured power is compared with the powerlimit to obtain a second comparison result. In accordance with thesecond comparison result indicating that the measured power does notexceed the power limit, an enabling signal is delivered to one powercontrol unit, causing the timing control circuit to send a signal to theoutlet and thereby permitting connection of additional loads to thepower system. The enabling signal is propagated to another power controlunit. In specific embodiments, the enabling signal is delivered using afirst keyline connecting the power control unit to a power managementcircuit, and the enabling signal is propagated using a second keyline,separate from the first keyline, connecting the power control unit toanother power control unit.

The foregoing has outlined, rather broadly, the preferred features ofthe present disclosure so that those skilled in the art may betterunderstand the detailed description of the disclosure that follows.Additional features of the disclosure will be described hereinafter thatform the subject of the claims of the disclosure. Those skilled in theart should appreciate that they can readily use the disclosed conceptionand specific embodiment as a basis for designing or modifying otherstructures for carrying out the same purposes of the present disclosureand that such other structures do not depart from the spirit and scopeof the disclosure in its broadest form.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 schematically illustrates a load distribution and managementsystem in accordance with a prior disclosure.

FIG. 2 schematically illustrates a load distribution and managementsystem with power supply units having random timers, in accordance withanother prior disclosure.

FIG. 3 schematically illustrates an enhanced load management anddistribution system in which a signal enabling activation of poweroutlets is propagated from one power control unit to another, inaccordance an embodiment of the present disclosure.

FIG. 4 is a flowchart schematically illustrating operation of anenhanced load management and distribution system in accordance with anembodiment of the disclosure.

FIG. 5 is a flowchart schematically illustrating startup of a systemaccording to an embodiment of the disclosure, in which no user devicesare plugged in.

FIG. 6 is a flowchart schematically illustrating startup of a systemaccording to an embodiment of the disclosure, in which user devices areplugged in.

FIGS. 7A and 7B are connected flowcharts schematically illustratingoperation of a system according to an embodiment of the disclosure in apower management mode.

DETAILED DESCRIPTION

As described in detail below, embodiments of the disclosure include apower distribution and management system with a strategically controlledre-connect function, including a power measurement device, powercontroller units, and outlets for delivering power to distributed loads.Operation of the system, in accordance with embodiments of thedisclosure, includes systematically connecting loads when power isavailable, in a controlled manner such that system power consumption canbe maintained below a prescribed maximum limit; the system maintainscontrolled power management without the need for manual intervention.

System Overview

A system according to an embodiment of the disclosure is shownschematically in FIG. 3. Power management circuit 51 includes a limitcomparator 55 which has an input corresponding to the power consumed bythe system 53 and another input corresponding to the maximum power limit54. The power management circuit distributes system power to a pluralityof power control units 52, 70, etc. via power keyline 12. Each powercontrol unit (e.g. power control unit 52) is connected to several poweroutlets 64, 66, 68. Each outlet has a power connection to the powercontrol unit, and a line 65, 67, 69 for transmitting a request for powerto the power control unit. As shown in FIG. 3, outlet 64 is associatedwith an enabling circuit 59 which receives a power request 65 and anenabling signal 60, and is connected to an outlet control 58 forcontrolling delivery of system power to the outlet. Each power controlunit has a timing control circuit 63 which sends appropriate enablingsignals 60, 61, 62 to the outlets 64, 65, 66 respectively. Timingcontrol circuit 63 is connected to a first ENABLE keyline 56 and asecond ENABLE keyline 57. Timing control circuit 63 receives the statusof the ENABLE keyline 56 as an input, and outputs an appropriate signalto the next power control unit 70 over the second ENABLE keyline 57.

An overview of operation of a system embodying the disclosure is shownin FIG. 4. The power management circuit monitors the system powerconsumption (step 401) and compares that power level to the power limit(step 402). If the power limit has not been reached, the first ENABLEkeyline is SET (step 403) and this signal is input to a power controlunit (step 404). The power control unit proceeds to evaluate the statusof the outlets in that unit. If there is a request for power at anoutlet, the outlet is enabled in accordance with that request (step 405)and a time delay begins as described in detail below. During the timedelay, the total power consumed continues to be monitored by the limitcomparator (step 406). If the power limit has not been reached, thestatus evaluation is repeated for each outlet of the power control unitsequentially (step 407). The ENABLE keyline signal SET is thenpropagated to the next power control unit (step 408). These steps arerepeated for each power control unit to the last power control unit inthe system (step 409).

If the total system power limit is reached (step 406), the ENABLEkeyline is reset (step 410). Unused outlets of the power control unitare immediately disabled (step 411) and evaluation of outlets whereconsumers have plugged in devices is immediately halted (step 412). TheRESET signal is propagated immediately through each of the power controlunits (step 413) to the last power control unit (step 414). The systemthen operates in the power management mode until the power consumptionlevel is sufficiently reduced to permit a transition to the enabledmode. Details of power management operation and the transition sequenceare also discussed in detail below.

System Enablement Without User Devices Plugged In

FIG. 5 schematically illustrates the procedure of enablement of thesystem when no user devices are plugged in, in accordance with anembodiment. Power management circuit 51 monitors the power consumed bythe system 53 and compares this power level to the maximum power limit54, using limit comparator 55 (step 501). When the limit comparator 55determines that the total power sensed has not reached the limit (step502), the ENABLE keyline 56 is SET (step 503). This signal is input topower control unit 52, and timing control circuit 63 accordinglyinitiates evaluation of the outlet states for outlets 64, 66, 68 (step504). Outlet 64 is enabled by signal 60 (step 506). The power controlunit monitors outlet 64 to determine whether power is being requested bya power request signal 65 (step 507); if not, enable signal 61 isactivated and the next outlet, outlet 66, is evaluated via power requestsignal 67 (step 508). This sequence continues until all outlets havebeen evaluated; the ENABLE signal SET is then propagated on ENABLEkeyline 57 (step 509), initiating the same sequence in the next powercontrol unit 70. This procedure continues to the last power control unitin the system.

System Enablement With User Devices Plugged In

FIG. 6 schematically illustrates the procedure of enablement of thesystem when at least one user device is plugged in, in accordance withan embodiment. Power management circuit 51 monitors the power consumedby the system 53 and compares this power level to the maximum powerlimit 54, using limit comparator 55 (step 601). When the limitcomparator 55 determines that the total power sense has not reached thelimit (step 602), the ENABLE keyline 56 is SET (step 603). This signalis input to power control unit 52, and timing control circuit 63accordingly initiates evaluation of the outlet states for outlets 64,66, 68 (step 604). Outlet 64 is enabled by signal 60 (step 606). Thepower control unit monitors outlet 64 to determine whether power isbeing requested by a power request signal 65 (step 607); if not, enablesignal 61 is activated and the next outlet (in this case outlet 66) isevaluated via power request signal 67 (step 608). If the outlet beingevaluated is the last outlet in the power control unit and the ENABLEkeyline is still SET, the ENABLE keyline signal is propagated to thenext power control unit (step 609).

If power is requested, the request is granted and outlet control 58causes power to be provided to the outlet (step 610). A timer is theninitiated (step 611) delaying evaluation of the next outlet by apredetermined interval. The delay time is long enough (e.g. 10 seconds)to permit the load at the outlet to reach full power and for the powermanagement circuit 51 to evaluate the total power consumed (step 612).The total power consumed continues to be monitored by the limitcomparator 55; if the power consumed 53 has not reached the maximumpower limit (step 613), the ENABLE keyline 56 remains SET. When thedelay time expires, if the ENABLE keyline 56 is still SET, the nextoutlet will be evaluated (step 614). If a user device is plugged intothe next outlet (in this case outlet 66) and a request 67 for power isactive, the same sequence is performed by the timing control circuit 63while the power management circuit 51 evaluates the total powerconsumed. If a user device is not plugged into an outlet (e.g. the nextoutlet 68), the timing control circuit evaluates that outlet without adelay. This sequence is repeated for all of the outlets connected to thepower control unit. If the outlet being evaluated is the last outlet inthe power control unit and the ENABLE keyline is still SET, the ENABLEkeyline signal is propagated to the next power control unit (step 615).

This procedure permits evaluation of the loads one at a time, therebyensuring that the system maximum power load is not exceeded. Inparticular, the ENABLE keyline signal is propagated from one powercontrol unit to another, as opposed to being transmitted to all powercontrol units at once. This ensures that, during a transition from RESETto SET of the ENABLE keyline, only one outlet is evaluated (with anample measurement time) and enabled before moving on to evaluate thenext outlet.

If the total system power has reached the limit, the ENABLE keyline 56is reset (step 616). This is propagated immediately through each of thepower control units 52, 70, etc. This ensures that when the system hasreached the maximum load limit, the unused outlets are disabled and theevaluation of consumer devices is halted. The system then enters powermanagement mode.

Normal Operation

Normal operation is characterized by the ENABLE keyline signal being SET(that is, enable mode). As a consumer connects a device to outlet 64, arequest for power 65 is initiated to the power control unit 52. If theENABLE keyline 56 is SET when the request for power is initiated, outletcontrol 58 enables power to the outlet and thence to the device. Nodelays are required, due to the ENABLE keyline being SET prior to therequest for power 65.

Power Management Operation

When the total system power as determined by the power managementcircuit 51 reaches the limit, the ENABLE keyline 56 is reset (step 616).The RESET signal input to a power control unit causes unused outlets tobe disabled (step 701) and evaluation of outlets to be halted (step702). The ENABLE signal RESET is propagated through each of the powercontrol units 52, 70, etc. (step 703) to the last control unit (step704).

The power management circuit continues to monitor the system powerconsumption (step 705). As the total power consumed falls below themaximum limit 54, as determined by limit comparator 55 (step 706), theENABLE keyline 56 is SET (step 707). The SET signal is input to powercontrol unit 52 (step, which starts the evaluation of the outlets 64,66, 68 connected to the power control unit (step 752). Outlets areenabled and evaluated one by one as described above (step 753). Eachoutlet is evaluated for the presence of a power request (step 754). Ifan outlet is not requesting power, the evaluation sequence proceeds tothe next outlet (step 759). If an outlet is requesting power thatpreviously had power (that is, the outlet was in use upon entering powermanagement mode) (step 755), power to that outlet is maintained (step756) and the sequence proceeds to the next outlet (step 757). If theoutlet being evaluated is the last outlet in the power control unit andthe ENABLE keyline is still SET, the SET signal is propagated to thenext power control unit via keyline 57 (steps 758, 760).

For each outlet that is requesting power that did not have power grantedprior to the maximum limit being reached, the timing control circuitcauses a delay as that outlet is activated (see FIG. 6, steps 610-611).When that time delay expires and if additional power is still available(steps 612-613), the SET signal is propagated to the next power controlunit (step 615). This signal will continue to propagate through thesystem until either the maximum power limit has again been reached, orthe end of the chain of power control units is reached while the systempower consumed remains below the limit.

Alternate Embodiments

In alternate embodiments, the ENABLE keyline 56, 57, etc. is not aphysical connection from one power control unit to another; acommunication bus may be provided to enable power control units one at atime. In still other embodiments, the power management circuit 51 may bea standalone unit integrated into a power management system that is partof an aircraft power distribution system, or be configured as anothermeans of controlling a measuring power.

While the disclosure has been described in terms of specificembodiments, it is evident in view of the foregoing description thatnumerous alternatives, modifications and variations will be apparent tothose skilled in the art. Accordingly, the disclosure is intended toencompass all such alternatives, modifications and variations which fallwithin the scope and spirit of the disclosure and the following claims.

I claim:
 1. A system for managing distribution of electrical power,comprising: a power management circuit including a device configured tomeasure power consumed by an electrical load, and a comparatorconfigured to compare the measured power with a power limit; a pluralityof power control units each including at least one outlet for deliveringpower to a load, a timing control circuit coupled to each said outlet,the timing control circuit configured to deliver an enabling signal toeach outlet individually with a time delay, a signal input, and a signaloutput; a first keyline connecting the power management circuit with thesignal input of one of said plurality of power control units; and asecond keyline connecting the signal output of said one of saidplurality of power control units with the signal input of another one ofsaid plurality of power control units, wherein each power control unitis configured to propagate a signal to another power control unit viathe second keyline.
 2. The system according to claim 1, wherein eachpower control unit further comprises a power input coupled to a powerkeyline connected to the power management circuit.
 3. The systemaccording to claim 2, wherein each power control unit further comprisesan outlet control device coupled to each said outlet and to the powerkeyline, for delivering power to the outlet in accordance with theoutlet being enabled.
 4. The system according to claim 1, wherein thefirst keyline is characterized as a first ENABLE keyline for deliveringone of a SET signal and a RESET signal, the second keyline ischaracterized as a second ENABLE keyline over which one of the SETsignal and the RESET signal, in accordance with the signal from thefirst ENABLE keyline, is propagated to another power control unit, andthe timing control circuit in a given power control unit provides theenabling signal to the outlet thereof in accordance with the SET signalbeing input to the power control unit.
 5. The system according to claim4, wherein a comparison indicating the measured power exceeding thepower limit causes a reset condition in which the RESET signal isdelivered to the first keyline.
 6. The system according to claim 5,wherein in said reset condition, outlets without a consumer deviceconnected thereto at initiation of the reset condition are preventedfrom being enabled.
 7. The system according to claim 1, wherein eachoutlet is configured to deliver a signal indicating a request for powerin accordance with a consumer device being connected to the outlet. 8.The system according to claim 3, wherein said power management circuitis a standalone unit.
 9. The system according to claim 3, wherein saidpower management circuit is integrated into an aircraft power managementsystem.
 10. The system according to claim 9, wherein said outlets areconsumer electrical outlets on an aircraft.